I upgraded my VCenter Operations Manager 5.0.3 to version 5.6 by using the Upgrade package.
Once the upgrade was complete, I registered VCenter Operations to my VCenter Server (version 5.0.0) by clicking on Update in VCenter Operations Administration.
It updated the registration successfully and the plug-in shows as installed in VCenter Plug In - Manager (VCenter Operations Manager version 5.6.0.923459 shows as Enabled in Plug Ins).
I see that the new license files are in C:\Program Files\VMWare\Infrastructure\VirtualCenter Server\licenses\site in the form of 5 new files by the name of license-vco-56-e1-51-201203
license-vco-56-e12-51-201203
license-vco-56-e2-51-201203
license-vco-56-e3-51-201203
license-vco-56-e4-51-201203
When I try to add my new license key (which I upgraded on MyVMware license portal to VCenter Operations Suite 5.6 Standard) on my VCenter 5.0.0 Server (in Administration/Licensing), I get "Invalid license key: License file not found".
In vpxd.log, I see: Unable to decode license XXXXX-XXXXX-XXXXX-XXXXX-XXXXX with error 5 using path dir://C:\Program Files\VMware\Infrastructure\VirtualCenter Server\licenses\site.
VCenter Server 5 Standard Version: 5.0.0 Build 455964
VCenter Operations Manager Version: 5.6.0 (upgraded from 5.0.3)